The paper deals with the study related to integration of Flywheel Energy storage system (FESS) to an already available model of parallel hybrid vehicle with pre- transmission torque coupling, i.e., replacing the conventional chemical battery with an equivalent mechanical battery. Advantages like high reliability, long cycle life, high energy storage capacity and deep discharge of an FESS can potentially enhance the performance of the hybrid vehicles. FESS employed for the analysis comprises an integrated flywheel homopolar inductor machine with High-frequency drive. The simulation results of an Electrically Peaking Hybrid (ELPH) are used as a base work in the present analysis. The ELPH model uses a control strategy to optimize the vehicle performance with a major concern for battery performance. The paper analyzes the performance of considered FESS model under the same control strategy and driving conditions. A MATLAB/SIMULINK model is used for the analysis of the vehicle for both urban and highway drives. Finally a comparison is drawn between the performance of the chemical battery, working in its best efficiency range, as a result of the applied control strategy, to that of the considered FESS. It is inferred from the simulated results that the performance of employed FESS is satisfactory in comparison to chemical batteries. It is therefore expected that FESS can be effectively employed in hybrid vehicles.